In the computer processing field, it is common to store data in a commercial database system and to retrieve such data using a computer system. It is also common to display such information in a variety of ways, each of which is suited for displaying a particular type or quantity of data. Many options are available for presenting data, especially with the advent of word processors, spreadsheets, and graphics software programs for creating tables and graphs.
In order to communicate information decisions effectively to users, designers need to understand the tasks in which readers engage when they look at displays. Because the user's tasks require certain sensory, perceptual and cognitive operations, one has to consider what type of information the user is trying to ascertain in reading the graph. For example, a well-designed line graph makes it easier to discern the slopes of lines, whereas, if the user's goal is to determine actual values at certain points, differentiating slopes is of little value.
There are various factors in making a decision about how to present data. The first factor concerns the amount of data being presented. When presenting a small amount of data, authors should weigh the communicative benefits of tabular or graphical presentation against the reader's cognitive costs. Generally, in this case, tabular presentation is preferred. However, with a large amount of data, the reader's use of the data, especially the degree of precision the reader is likely to need, becomes important. If relations are more important than precise values, then the data would probably be best displayed in a graph. Furthermore, readers with a general interest in a topic but no specific interest, may examine a graph to get the main idea. In contrast, readers who have done extensive work on a topic may examine the data in detail.
Finally, one must then choose the type of graph to present the information. This decision depends on both the characteristics of on the readers and of independent and dependent variables. Generally, common graphs with which all readers are likely to have experience are used: line graphs, bar graphs, pie charts, and scatter plots. The choice of graph type depends on the readers' informational needs. Either a line graph or a bar graph is used if readers need to determine relative or absolute amounts. A line graph is used if readers need to determine the rate of increase of the dependent (criterion) variable as a function of changes in the independent (predictor) variable. A bar graph is used if readers need to determine the difference between the means of the dependent variable across different levels of the independent variable. A pie chart is used if readers need to determine proportions but not absolute amounts.
Another important factor in the design of visual displays is the general relation between physical amount and perceived amount as a power function: perceived amount=a(physical amount).sup.b, known as Stevens' law. When the exponent b=1.0, the increase in perceived amount corresponds to the increase in the physical amount; when b&lt;1.0, the perceived amount increases more rapidly than the physical amount. Because the physical dimensions that display simple linear data extending in either vertical height or horizontal length produce Stevens' law exponents of 1.0, a reader's perception of the bar graphs and line graphs will accurately correspond to the physical distances shown in the graph. In contrast, the physical dimensions of the area of a rectangle or a circle and the volume of a cube typically produce exponents in Stevens' law of less than 1.0, resulting in an incorrect estimation of the size of indicators. Use of the lightness of shades of gray typically produces an exponent in Stevens' law of greater than 1.0.
As per the foregoing, it has always been a goal of the prior art to improve methods of displaying data in a graphically appealing format in order to allow a user to easily ascertain information by viewing the visual display. There is a need in the prior art for a method of displaying data such that relative amounts of data can be clearly visualized with an element of comparison included.
It is an object of the present invention to transmit as much information to the user in an organized manner such that the ease with which the user can view and understand the information is maximized.
It is an object of the present invention to display data such that a user can not only ascertain relative amounts within a set of data but also the relativity between multiple sets of data.
It is a further object of the present invention to provide a means to compare two sets of data corresponding to the same real world parameters with one variable change, such as time period.
It is a further object of the present invention to place this comparative graphic display on a graphic image of a map to add the further variable of geographic location.